


A Problem of Shapes

by Alaena_F_Dragonstar



Category: Magic Kaito, 名探偵コナン | Detective Conan | Case Closed
Genre: College, Comedy, Established Relationship, Humor, M/M, Post-Conan Kudou Shinichi, Potions Accident, Romance, Shapeshifting
Language: English
Status: Completed
Published: 2021-01-18
Updated: 2021-01-18
Packaged: 2021-03-16 20:14:14
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,464
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28836879
Author URL: https://archiveofourown.org/users/Alaena_F_Dragonstar/pseuds/Alaena_F_Dragonstar
Summary: When Shinichi took a cure for his cold from Koizumi Akako, he had not expected to find himself four-legged and furry. But the cat was only the beginning. He really should have listened to Kaito. KaiShin
Relationships: Kudou Shinichi | Edogawa Conan/Kuroba Kaito | Kaitou Kid
Comments: 2
Kudos: 88





	A Problem of Shapes

**Author's Note:**

> This was first posted on my FF.Net account [here](https://www.fanfiction.net/s/10506655/1/A-Problem-of-Shapes).

"Seriously Shin-chan, you need to work on your listening skills. How many times have I told you never to accept anything from Koizumi? But did you listen?"

Large, sapphire blue eyes glared balefully up at him. The face they were set in was small and furry with whiskers on, yet somehow they still managed to look disgruntled. The magician couldn't help it. He cracked up laughing.

Kudo Shinichi, former college detective now cat, huffed and turned his back on the magician. His newly acquired tail curled over his forepaws. He looked down at it and watched the tip swish. Curiously, he lifted a paw and prodded it. It felt incredibly weird that he could feel it. It really did belong to him.

So here he was, (possibly) cured of his cold, but less than two feet tall with a lustrous coat of black fur. The cold didn't seem so bad anymore.

He sighed then let out a mew of surprise as calloused hands wrapped around him, lifting him clear off the bench and depositing him on their owner's lap. Then those fingers began to scratch lightly behind his ears. A shiver ran down his spine.

Kaito grinned down at the purring cat. This certainly was going to be an interesting day.

Little did he know just how interesting it was going to get.

"Well, it's about time we headed to class," the magician was saying when the cat on his lap suddenly let out a soft 'shew' of a sneeze—and suddenly he wasn't petting a cat but a dog. It was only a little bit larger than the cat and the fur was just as soft if brown instead of black, but it was definitely a dog. He blinked.

Shinichi yawned and hopped onto the ground before giving himself a shake. That was when he noticed the odd look that he was receiving. He tilted his head questioningly. In response, Kaito produced a small mirror and held it before his now much longer muzzle. He sat down hard in surprise.

"Well, you could always come to class anyway," Kaito suggested, making the mirror disappear and rising from the bench. "Dogs have excellent hearing. You can lie outside the door and listen to the lecture."

Shinichi brightened. He liked that idea. Just because he wasn't currently human didn't mean he had to miss his classes. Unbeknownst to the detective, his tail had begun to wag.

Kaito swallowed a snigger, turning it into a cough. "Right then. Shall we be on our way?"

Shinichi stood up, shook himself, and started to trot in the direction of his physics class.

"Hold on, you can't just go like that," the magician called after him. "Dogs caught on campus without leashes and collars get sent to the pound."

Shinichi froze. He'd forgotten about that. If he could have sighed, he would have. Padding back to his partner, he sat down by the magician's feet and looked up at him questioningly.

"No need to worry," Kaito assured him. "I've got everything covered." He snapped his fingers and produced a collar and tag. The tag had "Shin-chan" engraved on one side and "If found, return to Kuroba Kaito" on the other.

Shinichi wondered briefly why the thief had such a thing readily on hand but decided that he really didn't want to know.

They had almost reached the building where the lecture would be held when they spotted Hakuba coming towards them from the opposite direction.

The blond detective stopped dead in his tracks at the sight of them. Kaito raised an eyebrow at the way Hakuba's face drained of all color.

"What's the matter with you?" he asked.

"Kuroba," the blonde began slowly, still not moving a muscle. "Is there a reason you are walking an alligator through our campus?"

Kaito blinked then looked down. Sure enough, where the dog had been there was now a small alligator. The collar was still around its neck. Hiding his own surprise behind his poker face, Kaito turned back to the blonde with a grin.

"This is my new pet. Isn't he cute?"

Hakuba twitched. "You can't bring something like that onto campus."

"He won't hurt anyone. See?" The magician knelt and patted the alligator on the head.

Hakuba's frown only deepened. "That's not the point. It's a dangerous animal."

"I assure you, he is not a dangerous animal."

Hakuba didn't look convinced, but Kaito didn't really care. He was more worried about getting Shinichi home before someone called animal control on them. Shinichi couldn't well go to class as an exotic reptile. Where no one would have said anything about a dog lying by the classroom door, an alligator…well, suffice to say things would be different.

So he tugged lightly on the leash to let Shinichi know it was time to start walking and tossed the blonde a jaunty wave farewell (with an additional smirk just to make the detective nervous).

He got a lot of strange looks walking with an alligator on a leash. But he was pretty sure it wasn't half as many strange looks as he would have gotten if he'd been walking with an alligator not on a leash. Fortunately, they reached their apartment without incident.

"Well, I guess we're stuck here until you change into something less toothy," he told the alligator as he removed the leash.

If he could have, Shinichi would have sighed. Instead he looked up at his partner and swished his tail. He felt guilty that the magician was skipping class on his account.

"Don't worry about it," Kaito said as though he'd read his mind. "It's just class. It was supposed to be review today anyway. This is more important. And yes, I know you can take care of yourself," he added, knowing exactly what his detective would say then. "But you've already been three different shapes in the last hour. We don't know what else that potion you should've known better than to drink might've done to you."

Unable to argue with that sentiment even had he been able to speak, Shinichi could only give in.

X

There really wasn't, Kaito mused, much that you could do with an alligator. Walks or any other type of outing were out of the question. Games…well, there were probably games out there somewhere that alligators could play, but Kaito would admit to being stumped, especially considering the limited room in the apartment. They couldn't converse, and alligators didn't seem to like being petted the way dogs and cats did. Shinichi had shaken his head when Kaito offered him food. So, in the end, they'd resorted to watching a movie.

Halfway through the movie, Kaito went to fetch himself a snack. He'd just finished slathering cream cheese on his bagel when he heard a strange noise from the living room followed by what sounded like a human voice grumbling.

"Shin-chan?" Bagel still in hand, he walked back into the living room.

"That was really weird," said a voice that sounded both like and a little unlike his detective's. And there, clambering up off the floor, was a slim and rather bare figure with a familiar cowlick.

Kaito almost dropped his bagel. "T—Tantei-kun?"

There was a strange note in the magician's voice that Shinichi had never heard in it before. Concerned, he turned fully to face the man in question. "Kaito?"

The thief opened his mouth then closed it again. No words emerged. His indigo gaze remained fixed on Shinichi like it was glued there. Shinichi gave him a confused look. If he didn't know better, he'd say that Kaito appeared embarrassed. But Kaito was never embarrassed. Shame was one word that simply didn't exist in the magician's vocabulary.

Following Kaito's gaze, Shinichi looked down at himself.

And suddenly he knew why Kaito had that look on his face. After all, flirt though he was, even Kaito would be embarrassed if unexpectedly faced with a living, breathing naked lady (the breathing part mattered, art thief that he was).

Flushing dark red, Shinichi hightailed it into the bathroom and slammed the door shut.

He caught a glimpse of himself in the mirror, blushed, and turned around so he had his back to it. Then he just stood there at a loss. He didn't know where to look or where to put his hands. Or should that be her hands now?

A knock came at the door. "Shinichi? Is everything okay in there?"

"That would depend on how you define okay," the detective replied, staring hard at the wall. "Um, could you…get me some clothes? It's a bit…awkward…like this."

"Well, I think we still have those clothes your mother sent you for your birthday if you haven't burned them. I'll go look."

There was the sound of a distant door opening then closing and Kaito was back at the door. "Would you like me to come in?"

"No! I mean, no," Shinichi amended. "Just pass it inside." Moving to the door, he unlocked it and opened it just enough to stick his arm out. A bag was pressed into his waiting palm and he drew it into the bathroom with him before relocking the door.

Inside the bag was the white and blue dress his mother had decided would make a wonderful birthday gift for her darling little Shin-chan. He was pretty sure she'd chosen the outfit because it matched Kaito's KID uniform, but she'd denied any motive beyond wanting to see her baby in something pretty. When Shinichi had insisted that he would not dress up just for her entertainment, Yukiko had cried about her son's lack of appreciation until he'd finally given in and tried the stupid dress on. That had been the one and only time he'd worn the thing. After his mother was appeased, he'd wrapped up the dress, stuffed it into the bag it had come in, and pushed the whole lot to the back of the wardrobe. How Kaito had found it again so quickly, he had no idea. But he supposed it was a good thing in this case.

Putting the clothes on was a bit of an ordeal. He had…new bits to deal with. It took him a whole five minutes to get the women's undergarments on properly because he kept stopping and blushing when his fingers brushed the bits he shouldn't have.

It was a very traumatized Shinichi who emerged from the bathroom to collapse onto the living room couch.

"What a day," he—she—groaned, burying his—her face in a couch cushion.

Kaito, who had quite recovered from the unexpected sight of his adorable Shin-chan in all her natural glory, laughed as he dropped onto the couch beside her. "Hey, at least you're human now. That's a step up, right?"

"I guess so," Shinichi agreed after a moment's thought. "At least I can do my work now."

Kaito rolled his eyes. "That's always what you think about first, isn't it? Well, I'm not going to interfere with your work, but before you run off after the next homicidal maniac that I'm sure we're going to hear about any minute, I would like to go out for lunch."

"…What?"

"A date, Shin-chan. I'm asking you to go to lunch with me before you go to work."

"Oh…but, I mean, I'm like this." Blushing, Shinichi waved a hand at his—herself. "Won't it be awkward?"

"Awkward?" Kaito repeated incredulously. "My dear Shinichi, why ever would it be awkward? It's still you in there. If you're worried about your appearance, I can assure you that you make a very pretty girl."

"That's not the point!" the detective spluttered, though the compliment brought a shade of pink to his cheeks. "What if people see us?"

"Then they see us. So what?"

"What if they recognize me?"

"They'll just think I dressed you up."

"…" That was probably true. Usually it would be true.

"It's not like people around here aren't used to seeing you get dressed up," Kaito continued, sounding like the voice of reason. And that, Shinichi thought, was a very frightening thing to hear.

And so here he—she was, sitting in a café booth across from his, no, her scheming boyfriend.

Kaito headed to the counter to pick up their orders. Left in their booth, Shinichi felt a sudden itch in the back of her nose. She quickly pinched her nose and the sneeze died before it could escape. Shinichi let out a sigh of relief. Awkward as it was to suddenly be a woman, he liked being human better than being a reptile.

"Oi there, Kudo! How're you doing?"

Shinichi froze at the familiar voice, not at all surprised when, a moment later, a dark-skinned teen appeared beside the table. He peered down at her with a good humored grin and a raised eyebrow. "Whoa, that is you, right?"

Shinichi took a sip from his coffee mug to give himself—herself some time to gather her wits before looking up and meeting Hattori's inquisitive gaze. "Yes, it's me. And if you laugh or make any kind of tasteless comment, I will tell Kaito that you tried to hit on me."

Heiji's face went pale—not an easy feat with his complexion—and laughed, raising placating hands. "No need ta go making threats. I wasn't gonna say anything like that. I was only thinking that you're looking pretty fun—I mean convincing. If I didn't know you weren't a girl, I'd have thought you'd been pulling the wool over all of us before."

"That might be because she is currently very much meant to be wearing that dress," Kaito supplied, making the two detectives jump. Neither had noticed his presence until that moment.

Heiji frowned at the magician. "What? What does that mean? You can't really mean that Kudo's been a girl all this time. Er, you can't, right…? I mean, I guess—"

Shinichi stomped on the stuttering detective's foot, causing him to cut himself off with a yelp.

"What was that for?" he demanded, glaring at her.

"For being stupid," Shinichi replied in a matter-of-fact tone. "I'm just…having some shape issues right now."

"…You mean like Conan?"

Shinichi blinked in mild surprise then nodded. "Yeah, I guess that's a pretty good comparison."

"You shoulda just said so from the start." The Osakan laughed heartily. "For a moment there, I seriously thought you were gonna say you've been a girl all along."

Not knowing what to say to that, Shinichi took his pasta from the tray Kaito had brought back. The magician handed over a bundle of utensils as well, eyes still twinkling with amusement.

"Heiji!" A girl with a ponytail appeared from out of the crowd of other customers and smacked the dark-skinned detective on the shoulder. "What're you doing here? You were supposed to be getting our drinks!"

"Ow, hey, I was just saying hello. Jeez Kazuha, give me a break."

"Saying hello?" The girl peered around him and down at the occupants of the table (who were currently eating like they weren't there). "Oh, oops. Hello Kuroba-kun, Ku…" She trailed off, frowning hard at Shinichi. Then, with an abruptness that was almost shocking, she leveled an accusing finger at Kaito and burst out with, "You! Don't tell me you're cheating on Kudo-kun!"

Kaito drew himself up in indignation. "I beg your pardon. I am doing no such thing."

Hattori burst out laughing then yelped as Shinichi kicked him hard on the shin. Kazuha just scowled and jabbed a finger at Shinichi.

"So then who's she? And what are you two doing here?"

"Two people can eat together without being on a date," Kaito drawled. "But if you must know, she's an exchange student from America. I've agreed to show her around campus."

"Oh." Kazuha let out a sheepish laugh and scratched at the back of her neck. "Sorry. My mistake." Turning, she held her hand out to Shinichi. "My name is Toyama Kazuha. I hope you enjoy your time here. And sorry again. I didn't mean to make a scene…"

"That's okay," Shinichi replied, shaking the proffered hand. "And thank you."

There was an awkward moment as Shinichi wondered if he should try to make up a name for himself—herself, but Heiji came to the rescue.

"We should be getting back to our table," he said, catching Kazuha's arm. "The food's gonna get cold if we don't."

With that, the two bid Kaito and Shinichi farewell. It wasn't until they had gone that the blue-eyed detective let out a sigh of relief.

Kaito chuckled. "Shall we get back to our own meal then?"

They managed to finish eating without any more interruptions. In fact, everything was going well until they stepped out of the café and ran smack into a woman carrying a large tray of salad. Letts leaves and shredded onions flew as cheese powder puffed over hands and faces.

Shinichi sneezed—and vanished.

Kaito felt a brief moment of panic as his gaze swept the ground. People around them screamed. But then he spotted movement under the discarded dress. Reaching down, he flipped the dress off of—

A blue and silver fish.

Kaito found himself faced with a sudden but serious dilemma. He hated fish—always had and probably always would. Those bug-eyed, scaly monstrosities were the embodiment of disgusting, and usually the sight of one flopping around on the ground would have him walking quickly the other way. This particular fish, however, wasn't just any fish. It was his detective. The same detective he'd vowed to protect with his life.

For one wild moment he hoped the fish would just sneeze and turn into something more pleasant, but then he realized that he didn't know if fish could sneeze. And if he didn't get Shinichi into water soon he'd suffocate.

It was the terrible thought that Shinichi would actually die if he didn't do something that had him gritting his teeth and diving forward to scoop the suffering fish from the ground.

"Water!" he shouted as he did so. "Someone get me a bucket or something!"

A hectic ten minutes later, Shinichi found himself swimming in circles around a small fish tank from a pet store that had been across the street from the restaurant where he and Kaito had had lunch. The shop owner was currently chatting with Kaito over said tank.

"I've never seen this species of fish before," the man was saying. "Where did you get it?"

"An old acquaintance from high school gave it to me," Kaito replied, hiding a scowl behind a pleasant smile. "She has a habit of finding unusual things."

"I don't suppose she mentioned what kind of fish this one was? I have some customers who would be most interested in fish with such vivid colors."

"I'm afraid she didn't say."

"Ah well, that's too bad. Hey, I don't suppose you'd consider selling me this one?"

Okay, it was definitely time to go. The magician put on a regretful face. "I'm sorry, but it would be a bit rude of me to sell a gift from a friend. Besides, I'm rather fond of this one."

The shopkeeper looked disappointed, but he didn't press the issue. "If you do find out what species it is, please let me know."

"I will. Thanks for the tank."

"No problem. If you ever need anything else, I also stock more tank decorations than any other shop in this area."

Kaito nodded and thanked the man again. Then, heaving the tank up in his arms, he marched off in search of one Koizumi Akako. If Shinichi was stuck as a fish, the witch was in for some serious payback from one furious phantom thief.

X

"Where's Koizumi?!"

Nakamori Aoko looked up from where she'd been working on her criminology class report at the sound of her childhood friend's voice. Her jaw dropped at the sight of him. "Kaito, is that a—"

"I want Koizumi," he snapped before she could finish the question. "Where is she?"

"I—I don't know. The last time I saw her was this morning when she left our dorm room," the inspector's daughter stammered, still staring at the sloshing tank the magician was holding. Inside it was a rather pretty blue and silver fish. "Um, are you all right?"

"I'm fine," the magician replied with a manic smile that made Aoko want to back away. "Why do you ask?"

"Uh…well…" Her gaze flickered down to the fish again before she gave up. "Never mind. I think you might try that outdoor tea place on the east side of campus. Akako likes to do her studying there. I believe she mentioned a test coming up, so chances are pretty high that she might be there now."

"Thanks."

Aoko watched Kaito go with a sense of foreboding. She hadn't liked that look in his eyes. Like cold fire. It would probably be best to stay out of his way for a while.

X

Kaito spotted the familiar rich crimson of his quarry's hair the moment he drew near the cluster of tables and chairs that served as one of the university's most popular places of study when the weather was good. It served a variety of teas and coffees in addition to assorted snacks. Kaito usually swung by the place for their excellent ice creams, but today he didn't so much as glance at the snack stand. Instead he stalked through the tables until he reached Akako's.

"Koizumi!"

The redhead looked up from a cup of tea with all the languid grace of a noblewoman with all the world at her beck and call. "Kuroba-kun. This is unexpected. You don't normally seek me out. To what do I owe this pleasure?"

"Don't play dumb," the magician snapped, plunking the tank down on the table right on top of the papers the witch had been reading. "What did you do to Shinichi?"

Ruby eyes blinked slowly at him before lowering to the tank and the fish swimming in circles inside. A look of surprise flickered across her face before it smoothed into one of interest. "Well, this certainly is most unusual. The potion was only meant to cure his cold."

"Oh yes, very cured," Kaito replied, sarcasm dripping liberally from every word. "So good to know this wasn't intentional. Skills getting a bit rusty, are they?"

Akako looked away. It seemed to Kaito that she might actually be embarrassed, but at the moment he couldn't care less. "The potion does tend to be a bit volatile. Although it is strange that it actually made him change shape. Shinichi-kun must be morphicaly unstable."

"And what the hell does that mean?"

"It means that his body is more susceptible to changing shape than your average human."

"Well change him back!"

"I can't."

Indigo eyes narrowed dangerously. "Excuse me?"

"It will have to wear off on its own," the witch hurried to explain. She wasn't the type to be easily cowed, but she knew when not to mess around. "If he took the potion immediately after I gave it to him then it shouldn't last beyond this evening."

"I see." Kaito took a moment to consider the situation. He was not happy at all, but if Akako said it would wear off then, for Shinichi's sake, he would just have to wait. "Fine then. Do you have anything that can make a fish sneeze?"

"Make a fish sneeze?" Akako raised an eyebrow. "I was not aware that fish could sneeze."

Scowling, Kaito picked the tank up once again and turned to go. But before he left, he gave the witch a last, menacing look. "You better hope nothing happens to Shinichi because of this."

X

Life as a fish was rather dull. Shinichi had long lost count of how many laps he'd swum around his tank. Well, tub now. After they'd gotten home, Kaito had covered the bottom of the bathtub with just enough fish-habitable water and pouted Shinichi into it.

"I doubt you'd want to change back in the tank," he'd said by way of explanation. He had also brought in a bundle of clothes so that Shinichi would have something to change into when he turned human again. Not being able to do much else for his poor fishy detective, he'd gone with the promise that he'd check in regularly. Shinichi was rather touched by the way Kaito had actually managed to overcome his hatred of fish for his sake. It made him feel both ridiculously happy and mildly guilty. He was happy to know that the magician thief cared for him so much, but he regretted having been so stupid as to get himself into this mess to begin with.

Shinichi sighed mentally and swam around the tub again.

Outside, Kaito checked the clock for the umpteenth time that day. It was already seven thirty. He supposed he should go get them some food. Should he buy Shinichi some fish food? Did you need to know what species a fish was to buy food for it?

For the first time in his life, Kaito lamented not knowing more about fish. Damn Koizumi.

"Um, Kaito?"

Jacket already in hand, Kaito turned around quickly at the sound of his name.

There, standing in the hall with his hair still damp and a mildly embarrassed expression, was Shinichi.

Kaito dropped his jacket and bounded forward, sweeping Shinichi off his feet and spinning the detective around. "Shin-chan! You're back to normal!"

"Kaito, put me down!"

Laughing, Kaito lowered Shinichi back to the ground but didn't let go. Instead, he leaned down and caught the detective's lips in a fierce kiss that had Shinichi clinging to him.

"I hope you've learned your lesson," he said, running his fingers through soft, black hair.

Shinichi let out a slightly breathless laugh. "I won't ask Koizumi-san for anymore cold cures."

"Good. Now let's go get something to eat."

Epilogue

It was three in the morning and the sky was still dark when Kaito sat bolt upright in bed. Turning on the lights with a snap of his fingers, he turned and threw the covers off of the bed. The motion elicited a whimper of complaint from the person lying beside him, who had immediately curled up against the cold.

Indigo eyes swept over Shinichi from head to toe before Kaito relaxed.

"Kai…?" Sleepy blue eyes blinked up at him. "Is something wrong?"

Letting out a short laugh, Kaito lay back down and pulled Shinichi against his chest. "No, everything's fine. I just had this nightmare where Akako turned you into a mermaid—er, well, not a mermaid, but yeah, I'm sure you get the idea."


End file.
